Amenorrhea is the absence of menstrual periods in a person of reproductive age. It can be classified into two main types:
Primary Amenorrhea: When menstruation has not started by age 15 or within five years of breast development, whichever comes first.
Secondary Amenorrhea: When menstruation stops for three or more consecutive months in someone who previously had regular menstrual cycles, or for six or more consecutive months in someone with irregular cycles.